FR: Il n'est personne qui ne sçache ce que c'est que le vol

Along similar lines but in older French, years ago in my research I came across this sentence :

"Il n'est personne qui ne sçache ce que c'est que le vol."

Now I am having a doubt. For years I have translated this as "There isn't anybody who does not know what theft is." But is that a negative "ne" before "sçache" or a pleonastic "ne" which leaves the sentence in the (weirdly) affirmative?? In the second case, it would mean exactly the opposite : "Nobody knows what theft is."

In older French, the "ne" provides the negation. So you end up with a pretty typical French double-negative sentence: "Nobody doesn't know what theft is" = "Nobody could possibly be ignorant of what constitutes theft" = "Everybody knows what theft is."